1. Field of the Invention
This invention relates in general to hydraulic couplings, and specifically to hydraulic couplings used in undersea drilling and production applications. More particularly, this invention involves a dummy undersea hydraulic coupling member that is used for protecting an opposing coupling member that is stationed subsea.
2. Description of Related Art
Subsea hydraulic couplings are old in the art. The couplings generally consist of a male member and a female member with sealed fluid passageways connecting therebetween. The female member generally is a cylindrical body with a relatively large diameter longitudinal bore at one end and a relatively small diameter longitudinal bore at the other. The small bore facilitates connections to hydraulic lines, while the large bore seals and slidingly engages the male member of the coupling. The male member includes a cylindrical portion at one end having an outer diameter approximately equal to the diameter of the large bore in the female member of the coupling. The male member also includes a connection at its other end to facilitate connection to hydraulic lines. When the cylindrical portion of the male member is inserted into the large bore of the female member, according to various embodiments of the device, fluid flow is established between the male and female members. Several couplings of this type are shown in patents owned by National Coupling Company, Inc. of Stafford, Tex.
In undersea drilling and production applications, the male member of the coupling may be connected to a manifold plate or other securement at a subsea location at the inside or outside of a well bore. In many cases, the male members are positioned so that the end or leading face of each member points vertically up from the sea floor. The female members, which also may be secured to a manifold plate, are moved into position over the male members and then lowered onto the male members by a diver or subsea vehicle, such as an ROV (remote operating vehicle). When the female members are positioned on the male members, hydraulic fluid flow typically is from the female member to the male member of each coupling. Typically, one or both of the coupling members have poppet valves.
Each poppet valve typically includes a conical valve face which seats, in the closed position, against a valve seat in the coupling member. The poppet valve opens to allow fluid flow, and closes against the valve seat within the bore to arrest the flow. Generally, the poppet valve is spring-biased to the closed position. The valve may include a valve actuator which may be a nose or stem extending from the apex of the valve face along the longitudinal axis of the poppet valve.
When the male and female coupling members are disconnected, the male coupling members typically remain subsea, and the female coupling members are retrieved. Frequently, well bores in which the couplings are positioned contain debris. The male member, which remains subsea when the coupling is disconnected, is subject to debris accumulating in exposed flow passages when it is disconnected from the female member. The debris may contaminate the hydraulic fluid or cause wear to the seals and sealing surfaces in the hydraulic couplings and hydraulic system. Additionally, the coupling members that remain subsea are subject to marine growth, sand, silt, and other mechanical impacts unless there is some form of protection.
To reduce or prevent damage to the coupling member remaining subsea, dummy coupling members have been used. A dummy coupling member mates with the opposing coupling member, but the dummy is not connected to hydraulic lines and therefore does not function to conduct hydraulic fluid through the system. Instead, the dummy coupling member protects the opposing coupling member when the hydraulic line through that coupling is not in use.
Typically, dummy undersea coupling members are the female coupling member because the male coupling member remains subsea. Dummy female coupling members may have one or more seals in a receiving chamber, and these seals engage the male member when the male member enters the receiving chamber. Dummy female coupling members also may have a bore and/or a vent passage extending between the receiving chamber and an outer surface of the dummy coupling member body. This allows trapped seawater and/or trapped air in the receiving chamber to escape out of the receiving chamber of the dummy coupling member when it engages the opposing coupling member. However, the bore or vent passage also may be subject to ingress of silt, debris, etc., with less effective protection of the opposing coupling member.
Unless the trapped seawater or air is allowed to escape from the receiving chamber, it may be very difficult or impossible to fully mate the dummy coupling to the opposing coupling member. Another undesirable consequence that may occur if trapped seawater or trapped air is not allowed to escape, is due to increased pressure that may force the poppet valve of the opposing coupling member open and allow the trapped seawater or trapped air to enter the hydraulic lines. Disconnecting the dummy coupling member from the opposing member also may be difficult due to hydraulic lock.
Thus, a dummy undersea hydraulic coupling member is needed to prevent debris and marine growth and other objects from damaging the coupling member remaining subsea, and which allows the dummy coupling member to be engaged and disengaged from the opposing member without resistance due to trapped seawater and/or trapped air.
U.S. Pat. No. 5,692,538 to Robert E. Smith III, assigned to National Coupling Company, Inc., does not show a dummy coupling member, but shows an undersea hydraulic coupling member having angled flow passages in the body of the male member to help prevent ingress of debris. When the female member is attached to the male member, hydraulic pressure through the angled flow ports and against the face of the poppet valve urges the poppet valve of the male member open to allow fluid to flow between the coupling members. The poppet valve in combination with the angled flow ports in the male member body help prevent ingress of debris, while allowing trapped hydraulic fluid pressure to bleed off when the coupling members are disconnected.
The present invention resides in a dummy undersea hydraulic coupling member having a water displacement expansion chamber and a piston for varying the volume of the water displacement expansion chamber in response to the pressures acting on the opposing faces of the piston. When the dummy coupling member is connected to an opposing coupling member subsea, seawater and/or air in the receiving chamber of the dummy is displaced by the opposing coupling member. That seawater and/or air enters the water displacement expansion chamber, and the piston allows the volume of that chamber to increase as a result of pressure from displaced seawater and/or air acting on the front face of the piston until the chamber reaches the volume required for a pressure equilibrium.
When the dummy coupling member is disconnected from the opposing coupling member subsea, seawater pressure acting on the back face of the piston tends to urge the piston to decrease the volume of the water displacement expansion chamber, thus allowing the trapped seawater and/or air to prevent a vacuum in the receiving chamber. The piston decreases the size of the water displacement expansion chamber until it reaches the volume required for a pressure equilibrium.